Since the cause, image and pathophysiology of different hepatic diseases are varied and involve numerous unknown factors, the present status is that it is very difficult to develop a therapeutic agent for these diseases.
At the present time, representative examples of medicines widely used for treating and preventing hepatic diseases and which are clinically appreciated include glycyrrhizin preparations. Although they are believed to be effective against hepatic disorder cirrhosis or hepatitis and for the postoperative protection of the liver, etc., their efficacy is not so strong and, what is worse, they exhibit steroidal side effects. Further, they are available in the form of an intravenous injection and are disadvantageously inactive when orally administered.
Accordingly, it has been eagerly desired to develop a medicine which is highly safe and will exhibit its effect even when orally administered.
Under the above-described circumstances, the present inventors have started exploratory researches with a view to developing a therapeutic agent for hepatic diseases.
As a result, they have found that the benzoquinone derivative which will be described hereinbelow will attain the object of the present invention.
Examples of benzoquinone derivatives which exhibit a pharmaceutical activity include those described in, e.g., Japanese Patent Laid-Open Nos. 223150/1987, 223150/1987 and 177934/1983.
The benzoquinone derivative disclosed in the Japanese Patent Laid-Open No. 223150/1987 is different from the compound (I) of the present invention in chemical structure and is believed to have an antiasthmatic activity, thus being different from the compound of the present invention also in its pharmaceutical activity.
Japanese Patent Laid-Open No. 177934/1983 discloses a benzoquinone derivative which is different from the compound of the present invention in both efficacy and chemical structure.
Japanese Patent Laid-Open No. 185921/1988 discloses a therapeutic agent for hepatic diseases which is different from the compound of the present invention in chemical structure.